1. Field of the Invention
The present invention relates generally to surgical implant devices and, more particularly, to implant devices utilized in procedures where rigid internal fixation of bone portions is desired.
2. Description of the Prior Art
Various devices and methods have been used in the prior art for the fixation of bones or bone portions. In the case of procedures wherein the fixation of delicate bones is required, fine metallic wires are secured through holes drilled in the bones. Wires and pins of somewhat greater diameter can also be inserted through the bones with an apparatus such as a wire driver which resembles a rotary power drill. Staples have been employed as well to fixate osteotomy sites. In the case of larger bones, particularly in the reduction of fractures, self-tapping bone screws are often inserted into drill holes to secure portions of the bone on either side of the fracture and enable healing to occur.
Where greater stabilization is required or where in the case of a fracture, for example, a substantial amount of stress will be placed on the fragmented bone portions because of the position of the fracture, the weight of the patient, the nature of athletic or other activity in which the patient wishes to engage, or similar factors, bone-fixating compression plates are often placed across the fracture line and are anchored by screws inserted through the plates and into the bone on either side of the fracture.
In the open reduction and internal fixation of a variety of fractures of the proximal femur and femoral neck, combination screw and plate devices have been utilized wherein a cavity in the femoral neck is reamed out and a plate is put against the outer surface of bone through which a large screw or bolt is inserted and screwed into the reamed-out cavity. The screw or bolt is attached to a plate which abuts against the cortex of the femur. The plate is anchored in the bone by smaller bone screws.
The use of prior art devices such as screws or screw and plate combinations where compression of bone portions, for example in the case of fractures, is required, has significant drawbacks. Bone screws are normally inserted through the cortex of a bone and secured in the relatively soft bony material in the medulla, and the primary compressing force is provided by threads of the screw gripping into the medulla and the head of the screw pressing against the cortex. Particularly in the case of osteoporotic bone, the bone screws frequently do not provide sufficient compression on the bone to reduce the fracture properly.
In addition, when bone screws are used, even in cases where the opposite cortex is purchased, a very large hole is created through the cortex and medullary bone which cannot be filled in with bony material while the screw is in position. If the screw is removed, the areas of the bone immediately surrounding the screw hole have a greater susceptibility to cracking or fracturing than normal bone, and the bone is not filled in by natural healing processes for a considerable amount of time.
There are a number of prior art devices specifically designed for reducing fractures of the femoral neck and for fixating the portions of the femur which lie on either side of the fracture. Aside from the screw and plate devices which have been mentioned previously, there are various bolt-like devices which can be inserted into the femoral neck through a drill bore, either alone or inside the tube of a compression plate and tube apparatus.
In certain of these devices, a central shaft is encased in a tube which is split at the end which will be inserted into the femur and, as the central shaft is screwed into the femur, the split ends of the tube diverge and grip into the medullary material surrounding the drill bore. These devices are complex to manufacture and do not provide a great deal of compressive force necessary to reduce the fracture, impact the bone fragments and immobilize the bone fragments with respect to each other.
Another prior art device used with femoral fractures comprises a central threaded shaft encased in a tube. At the top of the tube, the end which will be inserted into the femoral neck, there are vertical slots, and inside the tube adjacent to the slots are articulated blade-like members. When the central shaft is screwed into the tube towards the top end thereof, the blade-like members are pushed outward through the slots and lock into place. This device is also complex to manufacture and has a number of drawbacks in surgical applications. In order to ensure that no large portion of the device protrudes from the bore after the device has been inserted and the blades have been opened, the bit used to drill the bore is left in the bore while the femoral shaft is manually hammered towads the femoral head, such as with a mallet, until the operator feels that the fracture has been closed and the bone portions have been impacted. The length of the bore is then determined by reference to the length of drill bit that is inside the bone, a device with a length slighly greater than the length of the bore is then inserted and the blades are opened when the device is in place.
This procedure of impacting the bone fragments by hammering the femoral shaft towards the femoral head is dangerous; the blows of the mallet will frequently drive bone chips, which may surround the femoral head in the case of a fractured femoral neck, into the hip joint or other surrounding tissue. Moreover, the devices of numerous difficult lengths must be available so that a device can be chosen with a suitable length, corresponding to the length of the bore, so that no significant portion will protrude from the bore after the device is inserted.
None of the prior art devices utilized to reduce fractures generally, or femoral fractures specifically, can be constructed simply and yet provide a great deal of compression on a bone to reduce fractures and/or fixate bone portions. In addition, none of the prior art devices which can be utilized where a great deal of tensile strength is required are of such construction that any protruding portion of the device can be simply cut or clipped off and discarded, which would obviate the necessity for manufacturing devices of a wide variety of lengths and having a number of such devices available during surgery so that one of suitable length can be selected.